Heat exchanger arrangement for turbine engine

ABSTRACT

A turbine engine cooling arrangement includes a core passage for receiving a core flow for combustion, a first airflow source including a first passage adjacent the core passage for conveying a first airflow, and a second airflow source including a second passage adjacent the first passage for conveying a second airflow. A heat exchanger is thermally connected with the first passage and the second passage for transferring heat between the first airflow and the second airflow.

BACKGROUND OF THE INVENTION

This disclosure relates to cooling arrangements and, more particularly,to an air-to-air cooling arrangement for a gas turbine engine.

Gas turbine engines are known and used for propulsion in vehicles, suchas an aircraft. For example, a typical gas turbine engine includes acombustion section for combusting fuel and air to generate hotcombustion gases. The combustion gases expand in a turbine section toprovide rotational power that is used to propel the vehicle. Thecombustion gases are then discharged from of the engine through anexhaust nozzle.

Typically, the combustion is designed to occur in a particulartemperature range to maximize the efficiency of the engine. However, thetemperature at surfaces of engine components may be limited by thematerials that are used to construct the engine. For example, thesurface temperature in the combustor, turbine section, and exhaustnozzle cannot exceed the operating temperatures of the materials used toconstruct these components, although the temperature in the gas path ofthe combination gases may exceed this.

Accordingly, there is a need for a cooling method and arrangement thatmaintains the exhaust nozzle at a desirable temperature.

SUMMARY OF THE INVENTION

An example turbine engine cooling arrangement includes a core passagefor receiving a core flow for combustion, a first airflow sourceincluding a first passage adjacent the core passage for conveying afirst airflow, and a second airflow source including a second passageadjacent the first passage for conveying a second airflow. A heatexchanger is thermally connected with the first passage and the secondpassage for transferring heat between the first airflow and the secondairflow.

In one example, a turbine engine includes a core passage having acombustion section and a turbine section for receiving a core flow forcombustion. An engine inlet section divides inlet air into a firstbypass flow and a second bypass flow. A first bypass passage is locatedradially outwards of the core passage for receiving the first bypassflow. A second bypass passage is located radially outwards of the firstbypass passage for receiving the second bypass flow, and the heatexchanger is thermally connected with the first bypass passage and thesecond bypass passage for transferring heat therebetween.

An example method of providing cooling for use in a turbine engineincludes the steps of establishing a core flow for combustion, a firstairflow, and a second airflow. The first airflow includes a firsttemperature and a first pressure and the second airflow includes asecond temperature that is lower than the first temperature and a secondpressure that is lower than the first pressure. Heat is transferred fromthe first airflow to the second airflow to cool the first airflow. Inone example, the cooled first airflow is used to maintain a desiredtemperature of an exhaust section of the turbine engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows.

FIG. 1 illustrates selected portions of an example gas turbine engine.

FIG. 2 illustrates an example heat pipe for use in the gas turbineengine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates selected portions of an example gas turbine engine10, such as a gas turbine engine 10 used for propulsion. The gas turbineengine 10 is circumferentially disposed about an engine centerline 12.In this example, the engine 10 includes an inlet section 13 having afirst fan 14 a and a second fan 14 b. A compressor section 16, acombustion section 18, and a turbine section 20 are located downstreamfrom the inlet section 13.

The fan 14 b is decoupled from the fan 14 a, as disclosed for example incopending application (PA-2618). For example, the fan 14 b is mounted toan outer shroud (not shown) outboard of the fan 14 a to enable the fans14 a and 14 b to rotate at different speeds. In this example, the fan 14a is coupled in a known manner with the turbine section 20, such asthrough a low spool shaft of the engine 10. An electric drive may beused to drive the fan 14 b at a different speed than the fan 14 a. Inother examples, the engine 10 may be modified from the illustratedexample, depending on the type of engine and its intended use.

As is known, air compressed in the compressor section 16 is mixed withfuel that is burned in the combustion section 18 to produce hotcombustion stream that is expanded in the turbine section 20 to drivethe fans 14 a and 14 b. FIG. 1 is a somewhat schematic presentation forillustrative purposes only and is not a limitation on the disclosedexamples.

The example engine 10 includes a cooling arrangement 28 having a corepassage 30, a first airflow source 32, and a second airflow source 34that receive inlet air 37 that enters the engine 10. In this example,the first airflow source includes a first bypass passage 39 a, and thesecond airflow source 34 includes a second bypass passage 39 b. Theinlet section 13 divides the inlet air 37 between the core passage 30,the first bypass passage 39 a, and the second bypass passage 39 b. Thecompressor section 16, the combustion section 18, and the turbinesection 20 are included at least partially within the core passage 30.In the disclosed example, the first bypass passage 39 a is locatedradially outwards of the core passage 30 relative to the enginecenterline 12, and the second bypass passage 39 b is located radiallyoutwards of the first bypass passage 39 a relative to the enginecenterline 12.

The core passage 30, the first bypass passage 39 a, and the secondbypass passage 39 b each terminate at an engine exhaust section 36, suchas an exhaust nozzle. In this example, the engine exhaust section 36includes a convergent section 38 and a divergent section 40 fordischarging an exhaust flow from the core passage 30.

The first bypass passage 39 a includes a first outlet 42 located at thedivergent section 40 and another outlet 44 located axially forward ofthe divergent section 40 at the convergent section 38. Each of theoutlets 42 and 44 of the first bypass passage 39 a may include aplurality of film cooling slots 46 that provide a fluid connectionbetween the first bypass passage 39 a and the core passage 30.

The second bypass passage 39 b also includes an outlet 48 that islocated at the divergent section 40 of the engine exhaust section 36 andthat is axially aft of the outlets 42 and 44 of the first bypass passage39 a. It is to be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the normal operational attitude of the vehicle andshould not be considered otherwise limiting.

The cooling arrangement 28 also includes a heat exchanger 54 that isthermally connected with the first bypass passage 39 a and the secondbypass passage 39 b. In this example, the heat exchanger 54 includes aplurality of heat pipes 56 each having one end that is at leastpartially within the first bypass passage 39 a and another end that isat least partially within the second bypass passage 39 b. Alternatively,other types of heat exchangers may be used. Given this description, oneof ordinary skill in the art will recognize suitable types of heatexchangers to meet their particular needs.

In operation, the engine 10 receives inlet air 37 into the inlet section13. The inlet section 13 divides the inlet air into a core flow 60, afirst airflow 62, and a second airflow 64. The core flow 60 flowsthrough the core passage 30, the first airflow 62 flows through thefirst bypass passage 39 a, and the second airflow 64 flows through thesecond bypass passage 39 b. The core flow 60 is utilized for combustionwithin the combustion section 18.

The engine 10 utilizes the first airflow 62 and the second airflow 64for cooling the engine exhaust section 36. In the disclosed example, thefirst airflow 62 and the second airflow 64 have different associated airpressures and temperatures. For example, the first airflow 62 has afirst temperature and a first pressure, and the second airflow 64 has asecond temperature that is less than the first temperature and a secondpressure that is less than the first pressure. The difference intemperature and pressure may be controlled using the fans 14 a and 14 b,such as by controlling fan speed of each fan 14 a and 14 b.

The first airflow 62 and the second airflow 64 stream over the heatpipes 56 of the heat exchanger 54. The heat pipes 56 transfer heat fromthe first airflow 62 to the second airflow 64 to thereby cool the firstairflow 62. The cooled first airflow 62 is then discharged through theoutlet 42 to cool the divergent section 40 of the engine exhaust section36.

In the illustrated example, the obstruction caused by the heat pipes 56within the first bypass passage 39 a causes a natural pressure loss ofthe first airflow 62. The pressure loss provides the benefit of reducingliner blow-off loads to the divergent section 40. In some instances, itmay be possible to directly use the second airflow 64 for cooling;however, if the second pressure of the second airflow 64 is relativelylow, it may not be suitable for direct cooling of the engine exhaustsection 36, for example.

In the illustrated example, a portion of the first airflow 62 is alsodischarged through the outlet 44 to cool the convergent section 38. Thesecond airflow 64 is discharged through the outlet 48 at the divergentsection 40 to provide additional cooling of the divergent section 40.

The disclosed cooling arrangement 28 thereby utilizes the differenttemperature of the first and second airflows in the heat exchanger 54 toprovide cooled air to the divergent section 40 of the engine exhaustsection 36. Using air-to-air heat exchange in combination with the firstand second bypass flows may provide the benefit of avoiding oreliminating heat exchangers that utilize somewhat more complexcirculatory coolant systems. Additionally, the added cooling provided bythe “cooled” first airflow 62 may permit the use of other materialswithin the engine exhaust section 36. For example, the additionalcooling may allow the use of lighter weight or less expensive alloy ororganic composite materials.

As will now be described, at least the second airflow source 34 need notbe a bypass passage as in the previous example. FIG. 2 illustratesanother example in which like components are represented with likereference numerals. In this example, a gas turbine engine 100 includes asecond airflow source 134 having an external airflow scoop 102. Theexternal airflow scoop 102 extends radially outwards from an outerperimeter 104 of the engine 100, such as on an outer cowl or nacelle.The external airflow scoop 102 is connected with a passage 106 thatreceives an inlet airflow 137 that flows around the outer perimeter 104.

In operation, the inlet air 137 flows into the inlet section 13 andaround the outer perimeter 104 of the engine 100. The inlet section 13divides the inlet air 137 into a core flow 60 and a first airflow 62,and the external airflow scoop 102 directs at least a portion of theinlet airflow 137 into the passage 106 as a second airflow 164 that thenflows over the heat pipes 56 of the heat exchanger 54.

Similar to the example of FIG. 1, the first airflow 62 and the secondairflow 164 have different associated air pressures and temperatures andstream over the heat pipes 56 of the heat exchanger 54 to subsequentlycool the divergent section 40 of the engine exhaust section 36 aspreviously described.

FIG. 3 illustrates another example in which like components arerepresented with like reference numerals. In this example, a gas turbineengine 200 includes a second airflow source 234 having an auxiliarypower unit 202. For example, the auxiliary power unit 202 may be used toprovide compressed air to start the engine 200. In this regard, apassage 204 a connects the auxiliary power unit 202 to the engine 200. Avalve 206 is disposed within the passage 204 a. The valve 206 isoperative to direct flow through the passage 204 a between the engine200 and another passage 204 b that is thermally connected with the heatexchanger 54.

In operation, the inlet air 237 flows into the inlet section 13, whichdivides the inlet air 237 into a core flow 60 and the first airflow 62.The auxiliary power unit 202 produces a second airflow 262 that flowsthrough the passage 204 a. When the valve 206 is in a first position,the second airflow 262 continues to flow through the passage 204 a tothe engine 200 for the starting function. However, when the valve 206 ismoved to a second position, the second airflow 262 flows through thepassage 204 b and over the heat pipes 56 of the heat exchanger 54.

Similar to the example of FIG. 1, the first airflow 62 and the secondairflow 264 have different associated air pressures and temperatures andstream over the heat pipes 56 of the heat exchanger 54 to subsequentlycool the divergent section 40 of the engine exhaust section 36 aspreviously described.

Thus, as disclosed by the examples herein, the heat exchanger 54 may beused in combination with the first airflow 62 from the first airflowsource 32 and a second airflow (e.g., 62, 162, and 262) from a secondairflow source (e.g., 34, 134, and 234) to cool the divergent section 40of the engine exhaust section 36, or even other sections of an engine.As can be appreciated, the source of the second airflow is not limitedto any particular source and may be any airflow from any airflow sourcethat is relatively cooler than the first airflow 60.

FIG. 4 illustrates an example of one of the heat pipes 56. In thisexample, the heat pipe 56 includes a sealed hollow tube 70 that containsa coolant 72, such as water, ethylene glycol, methane, liquid sodium, orother suitable coolant. The heat pipe 56 includes a first end 74 that isthermally connected with the first bypass passage 32, and a second end76 that is thermally connected with the second bypass passage 34. Theinterior of the heat pipe 56 defines a cooling circuit 78 fortransporting the coolant 72 in an evaporated and liquid state. In thedisclosed example, the heat pipe 56 includes a porous material 80 thatfacilitates transport of the coolant 72, such as by using capillaryforces.

Operationally, the coolant 72 transfers heat from the warmer firstbypass flow 62 at the first end 74 to the relatively cooler secondbypass flow 64 at the second end 76. The coolant absorbs heat from thefirst bypass flow 62 and evaporates into vapor. The evaporated coolant72 then moves through the open central portion of the heat pipe 56toward the second end 76. At the second end 76, the second bypass flow64 cools the evaporated coolant 72 and condenses it into a liquid,thereby rejecting the heat into the second bypass flow 64. The porousmaterial 80 then transports the condensed coolant 72 using capillaryforces toward the first end 74 for another cooling cycle. In thismanner, the coolant transfers the heat from the warmer first bypass flow62 to the second bypass flow 64. Additionally, the heat pipe 56 providesthe benefit of passive heat transfer. That is, the heat exchanger 54operates without mechanical assistance, such as without a mechanicalpump or the like.

Although a combination of features is shown in the illustrated examples,not all of them need to be combined to realize the benefits of variousembodiments of this disclosure. In other words, a system designedaccording to an embodiment of this disclosure will not necessarilyinclude all of the features shown in any one of the Figures or all ofthe portions schematically shown in the Figures. Moreover, selectedfeatures of one example embodiment may be combined with selectedfeatures of other example embodiments.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this disclosure. The scope of legal protection given tothis disclosure can only be determined by studying the following claims.

1. A turbine engine cooling arrangement comprising: a core passage forreceiving a core flow for combustion; a first airflow source including afirst passage adjacent the core passage for conveying a first airflow; asecond airflow source including a second passage adjacent the firstpassage for conveying a second airflow; and a heat exchanger that isthermally connected with the first passage and the second passage fortransferring heat between the first airflow and the second airflow. 2.The arrangement as recited in claim 1, wherein the first airflowcomprises a first temperature and a first pressure, and the secondairflow comprises a second temperature that is less than the firsttemperature and a second pressure that is less than the first pressure.3. The arrangement as recited in claim 1, wherein the first passage islocated radially outwards of the core passage, and the second passage islocated radially outwards of the first passage, relative to the coreflow.
 4. The arrangement as recited in claim 1, wherein the firstpassage includes a first outlet located at a first exhaust sectionposition and the second passage includes a second outlet located at asecond exhaust section position that is axially aft of the first exhaustsection position relative to the core flow.
 5. The arrangement asrecited in claim 4, wherein the first exhaust section position and thesecond exhaust section position are located at a divergent section of anengine exhaust.
 6. The arrangement as recited in claim 5, wherein thefirst passage includes another outlet located axially forward of thefirst outlet.
 7. The arrangement as recited in claim 6, wherein theoutlet that is located axially forward of the first outlet is located ata convergent section of the engine exhaust.
 8. The arrangement asrecited in claim 1, wherein the heat exchanger comprises a plurality ofheat pipes each having a closed, sealed tube containing a coolant and acooling circuit for transporting the coolant between ends of the tube.9. The arrangement as recited in claim 8, wherein each of the pluralityof heat pipes includes a first end located at least partially within thefirst passage and a second end located at least partially within thesecond passage.
 10. The arrangement as recited in claim 1, furthercomprising an engine inlet dividing inlet air into the core flow, thefirst airflow, and the second airflow.
 11. The arrangement as recited inclaim 1, wherein the first airflow source comprises a first bypasspassage, and the second airflow source comprises a second bypass passagelocated radially outwards of the first bypass passage.
 12. Thearrangement as recited in claim 1, wherein the first airflow sourcecomprises a bypass passage, and the second airflow source comprises aram air scoop.
 13. The arrangement as recited in claim 1, wherein thefirst airflow source comprises a bypass passage, and the second airflowsource comprises an auxiliary power unit.
 14. A turbine enginecomprising: a core passage including a combustion section and a turbinesection for receiving a core flow for combustion; an engine inletsection for dividing inlet air into the core flow, a first bypass flow,and a second bypass flow; a first bypass passage that is radiallyoutwards of the core passage for receiving the first bypass flow; asecond bypass passage radially outwards of the first bypass passage forreceiving the second bypass flow; and a heat exchanger that is thermallyconnected with the first bypass passage and the second bypass passagefor transferring heat between the first bypass flow and the secondbypass flow.
 15. The turbine engine as recited in claim 14, wherein theengine inlet includes at least one fan.
 16. The turbine engine asrecited in claim 14, wherein the first bypass flow comprises a firsttemperature and a first pressure, and the second bypass flow comprises asecond temperature that is less than the first temperature and a secondpressure that is less than the first pressure.
 17. The turbine engine asrecited in claim 14, further comprising an exhaust for receiving thecore flow, the exhaust having a convergent section and a divergentsection located aft of the convergent section.
 18. The turbine engine asrecited in claim 17, wherein the first bypass passage includes a firstoutlet and the second bypass passage includes a second outlet, whereinthe first outlet is located at the convergent section and the secondoutlet is located at the divergent section.
 19. A method of providingcooling air for use in a turbine engine, comprising: establishing a coreflow for combustion, a first airflow and a second airflow, the firstairflow having a first temperature and a first pressure and the secondairflow having a second temperature that is lower than the firsttemperature and a second pressure that is lower than the first pressure;transferring heat from the first airflow to the second airflow to coolthe first airflow; and cooling an engine component using the firstairflow.
 20. The method as recited in claim 19, further includingdischarging the first airflow from a first outlet that is located at afirst exhaust section position and discharging the second airflow from asecond outlet that is located at a second exhaust section position thatis axially aft of the first exhaust section position relative to thecore flow.